1. Field of the Invention
The present invention relates to an aqueous dispersion composition for chemical mechanical polishing for use in the manufacture of semiconductor devices (hereunder referred to as xe2x80x9caqueous dispersion composition for chemical mechanical polishingxe2x80x9d, or sometimes simply as xe2x80x9caqueous dispersion compositionxe2x80x9d). More specifically, the invention relates to an aqueous dispersion composition for chemical mechanical polishing that, for polishing of different types of working films and barrier metal layers formed on semiconductor substrates, can accomplish efficient polishing particularly of barrier metal layers and can give adequately flattened and high precision finished surfaces.
2. Description of the Prior Art
A recent technique used in the manufacture of semiconductor devices is a process whereby a wiring material such as tungsten, copper or the like is embedded in a hole or groove formed in an insulating film on a processing wafer and then polishing is performed to remove the wiring material above the surface of the insulating film to thereby complete formation of the wiring. Wiring formed by this process is called damascene wiring. This polishing cannot be very efficiently achieved on barrier metal layers made of metals with high hardness such as tantalum and the like. On the other hand, relatively soft wiring materials such as copper are easy to polish but exhibit dishing in the wiring sections, making it difficult to produce flat finished surfaces. In cases with a high pH, particularly with porous insulating films of low dielectric constant, the insulating film is excessively polished making it impossible to form satisfactory damascene wiring.
[Problems to Be Solved by the Invention]
The present invention solves the aforementioned problems of the prior art by providing a useful aqueous dispersion composition for chemical mechanical polishing in the manufacture of semiconductor devices, which is able to polish barrier metal layers made of tantalum and the like with sufficient rate, which gives sufficiently flat finished surfaces without excessively polishing wiring materials made of copper or the like or excessively polishing insulating films, and which can form satisfactory damascene wiring.
[Features of the Invention]
The aqueous dispersion composition for chemical mechanical polishing of the present invention is characterized by comprising a polishing agent, water and a polishing rate adjustor.
More, the aqueous dispersion composition for chemical mechanical polishing for use in the manufacture of semiconductor devices according to the another present invention, is characterized by comprising a polishing agent, water and a polishing rate adjustor, wherein, when polishing a copper film, a tantalum layer and/or tantalum nitride layer and an insulating film under the same conditions, the ratio (RCu/RTa) between the polishing rate of the copper film (RCu) and the polishing rate of the tantalum layer and/or tantalum nitride layer (RTa) is no greater than {fraction (1/20)}, and the ratio (RCu/RIn) between the polishing rate of the copper film (RCu) and the polishing rate of the insulating film (RIn) is from 5 to ⅕.
[Effect of the Invention]
According to the invention it is possible to obtain a useful aqueous dispersion composition for chemical mechanical polishing by preparing an aqueous dispersion composition containing a polishing rate adjustor.
By specifying the ratio between the polishing rates of for a copper film and a tantalum layer and/or tantalum nitride layer and the ratio between the polishing rates for a copper film and an insulating film, it is possible to polish barrier metal layers at a sufficient rate, to polish working films at an appropriate rate and to obtain an aqueous dispersion composition for chemical mechanical polishing which is useful for the manufacture of semiconductor devices, without excessive polishing of insulating films and without dishing.
Moreover, by specifying the function of the polishing rate adjustor or the type of polishing rate adjustor, and by specifying the pH, it is possible to easily obtain an aqueous dispersion composition for chemical mechanical polishing according to the invention.
[Means for Solving the Problems]
As a result of research with the object of obtaining an aqueous dispersion composition for chemical mechanical polishing that can achieve adequate flattening of finished surfaces for polishing of working films formed on semiconductor substrates, it was found that by including a polishing rate adjustor comprising a heterocyclic compound with an amino group and the like, it is possible to accelerate polishing of barrier metal layers, inhibit polishing of wiring materials such as copper, and to obtain adequately flattened and highly precise finished surfaces without excessive polishing of insulating films. The present invention has been accomplished on the basis of this finding.
This object is achieved firstly by an aqueous dispersion composition containing a polishing rate adjustor. The object is achieved secondly by an aqueous dispersion composition for chemical mechanical polishing with a specified ratio between the polishing rates of a copper film and a tantalum layer and/or tantalum nitride layer and between the polishing rates of a copper film and an insulating layer. The object is achieved thirdly by an aqueous dispersion composition containing a polishing rate adjustor with a specific function. The object is achieved fourthly by an aqueous dispersion composition containing a specific heterocyclic compound as the polishing rate adjustor. The object is achieved fifthly by an aqueous dispersion composition with a specific pH.
The aqueous dispersion composition for chemical mechanical polishing of the present invention is characterized by comprising a polishing agent, water and a polishing rate adjustor.
More, the aqueous dispersion composition for chemical mechanical polishing for use in the manufacture of semiconductor devices according to the another present invention, is characterized by comprising a polishing agent, water and a polishing rate adjustor, wherein, when polishing a copper film, a tantalum layer and/or tantalum nitride layer and an insulating film under the same conditions, the ratio (RCu/RTa) between the polishing rate of the copper film (RCu) and the polishing rate of the tantalum layer and/or tantalum nitride layer (RTa) is no greater than {fraction (1/20)}, and the ratio (RCu/RIn) between the polishing rate of the copper film (RCu) and the polishing rate of the insulating film (RIn) is from 5 to ⅕.
The copper which may form the xe2x80x9ccopper filmxe2x80x9d includes not only pure copper, but also alloys containing at least 95 wt % copper, such as copper-silicon, copper-aluminum and the like. The tantalum which may form the xe2x80x9ctantalum layerxe2x80x9d is also not limited to pure tantalum, and includes tantalum-containing alloys such as tantalum-niobium. The tantalum nitride which may form the xe2x80x9ctantalum nitride layerxe2x80x9d is also not limited to pure products.
The phrase xe2x80x9cunder the same conditionsxe2x80x9d used above means that the same polishing apparatus model is used, and the disk and head rotation rate, the polishing pressure, the polishing time, the type of polishing pad used and the rate of supply of the aqueous dispersion composition per unit of time are all consistent.
The xe2x80x9cratioxe2x80x9d of the polishing rates referred to above can be calculated from the respective polishing rates obtained by separately polishing a copper film, a tantalum layer and/or tantalum nitride layer and an insulating film, under the same conditions. The polishing may be carried out using a wafer provided with the copper film, tantalum layer and/or tantalum nitride layer or insulating film.
The ratio (RCu/RTa) between the polishing rate of a copper film (RCu) and the polishing rate of a tantalum layer and/or tantalum nitride layer (RTa) is preferably no greater than {fraction (1/30)}, especially no greater than {fraction (1/30)} and most preferably no greater than {fraction (1/50)}. If RCu/RTa is greater than {fraction (1/20)}, tantalum layers cannot be polished with sufficient rate, and when the aqueous dispersion composition is used for polishing of working films or barrier metal layers formed on semiconductor substrates, a longer time will be required for polishing of barrier metal layers in the second stage of a two-stage polishing process.
The ratio (RCu/RIn) between the polishing rate of a copper film (RCu) and the polishing rate of an insulating film (RIn) is preferably 4 to xc2xc, especially 3 to ⅓ and most preferably 2 to xc2xd. If RCu/RIn is greater than 5, excessive polishing of copper films may occur, and when the aqueous dispersion composition is used for polishing of working films formed on semiconductor substrates, dishing may be produced at the wiring sections, making it impossible to achieve a finished surface with sufficient flatness and high precision. On the other hand, if RCu/RIn is less than ⅕, excessive polishing of insulating films may occur, making it impossible to form satisfactory damascene wirings.
The xe2x80x9cpolishing agentxe2x80x9d referred to above may be used inorganic particles of silica, alumina, ceria, zirconia, titania or the like. The inorganic particles are most preferably synthesized by a gas phase process. Inorganic particles obtained by gas phase processes are most preferably particles synthesized by a fumed process (high-temperature flame hydrolysis) or a process by Nanophase Technology Co. (metal vapor deposition oxidation).
The inorganic particles used are preferably colloidal silica, colloidal alumina, colloidal titania or the like synthesized by (1) a sol method involving synthesis by hydrolysis and condensation of a metal alkoxide such as tetraethoxysilane or a titanium alkoxide or the like, or (2) an inorganic colloid method and the like in which the impurities are removed by purification.
The polishing agent used may be organic particles comprising thermoplastic resins such as polyvinyl chloride; polystyrene and styrene-based copolymers; polyacetals; saturated polyesters; polyamides; polycarbonates; polyolefins and olefin-based copolymers such as polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene and the like; phenoxy resins; (meth)acrylic resins such as polymethyl methacrylate; as well as acrylic-based copolymers. There may also be used organic particles comprising thermosetting resins such as epoxy resins, urethane resins and the like.
These inorganic particles and organic particles may be used alone or in combinations of two or more types, and inorganic particles may also be used in combination with organic particles.
The polishing agent may also be used organic/inorganic composite particles. Organic/inorganic composite particles need only be integrally formed to such an extent so that the organic particles and inorganic particles do not easily separate during polishing, and there are no particular restrictions on their type or structure.
The composite particles used may be prepared by polycondensation of an alkoxysilane, aluminum alkoxide, titanium alkoxide or the like in the presence of polymer particles of polystyrene, polymethyl methacrylate or the like, and bonding of polysiloxane or the like on at least the surface of the polymer particles. The resulting polycondensate may be directly bonded to the functional group of the polymer particles, or it may be bonded via a silane coupling agent.
The polycondensate does not necessarily need to be chemically bonded to the polymer particles, and the three-dimensionally formed polycondensate may by physically held on the surface of the polymer particles. Silica particles or alumina particles or the like may also be used instead of an alkoxysilane and the like. These may also be held by intertwining with the polysiloxane and the like. They may also be chemically bonded to the polymer particles by their functional groups, such as hydroxyl group and the like.
In an aqueous dispersion composition containing organic particles and inorganic particles with zeta potentials of opposite signs, the composite particles used may have their particles bonded by electrostatic force.
The zeta potentials of polymer particles are usually negative across the entire pH range, or across a wide pH range except for the low pH range; however, by using polymer particles with carboxyl groups, sulfonic acid groups or the like, it is possible to obtain polymer particles with a more definite negative zeta potential. Polymer particles with amino groups and the like have a positive zeta potential in specific pH ranges.
However, the zeta potentials of inorganic particles are highly pH-dependent and have an isoelectric point at which the potential is zero; the sign of the zeta potential reverses at around that point.
Thus, by combining specific organic particles and inorganic particles and mixing them in a pH range at which their zeta potentials are opposite signs, it is possible to form an integral composite of the organic particles and inorganic particles by electrostatic force. During the mixing, the zeta potentials may be of the same sign, and the pH adjusted thereafter to give zeta potentials of opposite signs, thereby allowing integration of the organic particles and inorganic particles.
The composite particles used may be prepared by polycondensation of an alkoxysilane, aluminum alkoxide, titanium alkoxide or the like in the presence of particles integrally composed in this manner by electrostatic force, and bonding of polysiloxane or the like on at least the surface of the particles to form a composite.
The composite particles used may be of one type, or they may be a combination of two or more types. The composite particles may also be used in combination with either or both inorganic particles and organic particles.
The mean particle size of the inorganic particles and organic particles is preferably 0.01-3 xcexcm. A mean particle size of less than 0.01 xcexcm will tend to reduce the polishing rate. On the other hand, a mean particle size of greater than 3 xcexcm may result in precipitation and separation of the polishing agent, hampering efforts to achieve a stable aqueous dispersion composition for chemical mechanical polishing. The mean particle size is more preferably 0.05-1.0 xcexcm, and even more preferably 0.1-0.7 xcexcm, since a polishing agent with a mean particle size in this range can give a stable aqueous dispersion composition for chemical mechanical polishing that allows polishing of barrier metal layers at a sufficient rate without precipitation and separation of the particles. The mean particle size may be measured by observation under a transmission electron microscope.
The polishing agent content may be 0.05-15 parts, but is preferably 0.1-8 parts and more preferably 0.5-6 parts, to 100 parts of the aqueous dispersion composition for chemical mechanical polishing. If the polishing agent content is less than 0.3 part it may not be possible to achieve a sufficient rate of polishing, while its content is preferably not more than 15 parts because the cost will be increased and the stability of the aqueous dispersion composition for chemical mechanical polishing will be reduced.
According to the invention, the polishing rate adjustor inhibits polishing of copper films and accelerates polishing of tantalum layers and/or tantalum nitride layers.
By including a polishing rate adjustor with this specific function, it is possible to easily obtain an aqueous dispersion composition for chemical mechanical polishing with the specific polishing ratio according to the invention.
The polishing rate adjustor used may be a derivative of a heterocyclic compound with an amino group, a mercapto group, a short-chain alkyl group of 1-3 carbons or the like.
As such derivatives there may be mentioned derivatives of compounds with heteropentacycles such as benzothiazole, benzothiadiazole, benzotriazole, triazaindolizine and the like, and compounds of heterohexacycles such as diazine, triazine and the like.
As derivatives of compounds with heteropentacycles there may be mentioned, in addition to the above compounds, 2-aminobenzothiazole, 2-amino-6-methylbenzothiazole, 2-mercaptobenzothiazole, 4-amino-1,2,4-triazole, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 3-mercapto-4-methyl-4H-1,2,4-triazole, 7-hydroxy-5-methyl-1,3,4-triazaindolizine, bismuthiol, adenine and the like.
There may also be mentioned 5-amino-1H-tetrazole, 2-mercaptothiazoline, guanine, 1-phenyl-5-mercapto-1H-tetrazole, 1H-tetrazole, 1H-tetrazole-1-acetic acid, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole, 4,5-dicyanoimidazole, 2-amino-4,5-dicyano-1-imidazole, 3H-1,2,3-triazolo[4,5-b]pyridin-3-ol, tolyltriazole, benzimidazole, benzofuroxane, benzo-1,2,3-thiadiazole and the like.
As derivatives of compounds with heterohexacycles there may be mentioned 3-amino-5,6-dimethyl-1,2,4-triazine, 2,4-diamino-6-diallylamino-1,3,5-triazine, benzoguanamine, thiocyanuric acid, melamine, 3-amino-5,6-dimethyl-1,2,4-triazine, phthalazine and 2,3-dicyano-5-methylpyrazine.
As polishing rate adjustors there may also be used derivatives of compounds with a heteropentacycle and a heterohexacycle. Such derivatives include adenine and guanine and the like.
Preferred among these polishing rate adjustors are 5-amino-1H-tetrazole, guanine, 3-mercapto-1,2,4-triazole, 1-phenyl-5-mercapto-1H-tetrazole, 5-methyl-1H-benzotriazole and 7-hydroxy-5-methyl-1,3,4-triazaindolizine and the like, which are mentioned in claim 3 or 11.
An especially preferred polishing rate adjustor is 5-amino-1H-tetrazole or 7-hydroxy-5-methyl-1,3,4-triazaindolizine.
The polishing rate adjustor content may be 0.001-3 parts by weight (hereunder referred to simply as xe2x80x9cpartsxe2x80x9d), preferably 0.01-3 parts and more preferably 0.05-3 parts, to 100 parts of the aqueous dispersion composition for chemical mechanical polishing. If the polishing rate adjustor content is less than 0.001 parts, it may not be possible to achieve a sufficient rate of polishing for tantalum layers and/or tantalum nitride layers, while a longer polishing time will be required when the aqueous dispersion composition is used for polishing of barrier metal layers formed on semiconductor substrates. On the other hand, a polishing rate adjustor content of 3 parts will adequately provide the desired effect, and there is no need for a higher content.
The invention of claim 7 or 15 specifies the recommended pH range for the aqueous dispersion composition for chemical mechanical polishing.
The pH of the aqueous dispersion composition is preferably from 1 to 10. With a pH in this range it is possible to inhibit polishing of insulating films in order to prevent excessive polishing of insulating films. The pH is preferably 1-9, more preferably 2-8 and especially 3-7.5. If the pH of the aqueous dispersion composition for chemical mechanical polishing is lower than 1 or higher than 10, excessive polishing may occur on porous insulating films of low dielectric constant, such as insulating films composed mainly of silsesquioxane, thus making it impossible to form a satisfactory damascene wiring.
The pH may be adjusted with an inorganic acid such as nitric acid, sulfuric acid or phosphoric acid, or an organic acid such as formic acid, acetic acid, oxalic acid, malonic acid, succinic acid or benzoic acid or the like.
When the pH is at the acidic end, the polishing rate on copper films is slowed while the polishing rate on tantalum layers and/or tantalum nitride layers is accelerated. When such an acidic aqueous dispersion composition is used for polishing of a working film formed on a semiconductor substrate, it is possible to achieve more balanced polishing of the working film and the barrier metal layer. The aqueous dispersion composition is particularly useful for polishing in the second stage of a two-stage polishing process. On the other hand, when the pH is near neutral, the polishing rate on copper films is accelerated while the polishing rate on tantalum layers and/or tantalum nitride layers is slowed. The barrier metal layer therefore functions adequately as a stopper layer. Such a neutral aqueous dispersion composition may be used for polishing even in the first stage of a two-stage polishing process.
The aqueous dispersion composition for chemical mechanical polishing of the invention normally contains no oxidizing agent. This is because an oxidizing agent accelerates polishing of working films such as copper films while resulting in a slower polishing rate for barrier metal layers. However, an oxidizing agent may be included so long as the oxidizing agent and its content are such that the ratio of the polishing rate for copper films and tantalum layers and/or tantalum nitride layers is within the range specified by the invention. As specific examples of oxidizing agents there may be mentioned hydrogen peroxide; organic peroxides such as peracetic acid, perbenzoic acid and tert-butylhydroperoxide and the like; and nitric acid compounds such as nitric acid, iron nitrate and the like. In addition to these oxidizing agents various additives may also be included as necessary. This can further improve the stability of the dispersion composition, increase the polishing rate, and adjust the difference in polishing rates when polishing films of different hardness, such as in the case of polishing two or more types of working films.
According to the invention, the ratio of the polishing rates for copper films and tantalum layers and/or tantalum nitride layers is specified, but the aqueous dispersion composition for chemical mechanical polishing of the invention can be used for polishing of various types of working films and barrier metal layers formed on semiconductor substrates in manufacturing processes for semiconductor devices such as super LSIs and the like. Such working films include pure copper films, pure aluminum films and pure tungsten films and the like, as well as films made of alloys of copper, aluminum, tungsten and other metals. Among these types of working films, the aqueous dispersion composition of the invention is particularly useful for polishing of films with low hardness, such as pure copper film and the like. Barrier metal layers include metals such as tantalum, titanium and the like, as well as their oxides and nitrides.
Barrier metal layers are usually formed by one type of metal such as tantalum or titanium or the like, but they sometimes include tantalum and tantalum nitride on the same substrate.
The polishing of the working film or barrier metal layer of a semiconductor device can be accomplished using a commercially available chemical mechanical polishing apparatus (such as Model xe2x80x9cLGP510xe2x80x9d or xe2x80x9cLGP552xe2x80x9d by Lapmaster SFT).
For the polishing, the residual polishing agent on the polishing surface is preferably removed after the polishing. The polishing agent removal may be accomplished by a common washing method, but in the case of organic particles it may be accomplished by burning off the particles on the polishing surface at high temperature in the presence of oxygen. The burning method may involve exposure to oxygen plasma, or ashing treatment by plasma with a supply of oxygen radicals in a downflow, whereby the residual organic particles on the polishing surface can be easily removed.
Above-mentioned xe2x80x9csemiconductor devicexe2x80x9d is used in a wide sense to include polished wafers, various devices provided with or bearing such wafers, plates manufactured from such wafers, and various devices provided with such plates (i.e., devices on which such plates are mounted).
[Preferred Mode of the Invention]